A sewage treatment plant was officially put into operation in June 1992, with secondary biochemical treatment, traditional activated sludge process and blast aeration. During the operation of 14, the factory has always been committed to strengthening process control to ensure that the effluent reaches the standard, which has made due contributions to water pollution control. At the same time, a series of problems have been found in the operation. In practice, through the efforts of technicians, corresponding improvements have been made to ensure that the old factory can play its due role.
2. Existing problems and countermeasures
2. 1 problems and solutions of grid decontamination machine grid is the key process in pretreatment process. Its function is to intercept and remove larger solid substances, and at the same time protect the sewage pump in the subsequent process, reduce the floating objects in the primary sedimentation tank and prevent the process pipeline from being blocked. The original design of this factory has only one grille with a gap of 25mm, which belongs to the medium and coarse grille type. There are four disadvantages:
(1) The drainage facilities in the service area are combined with rain and sewage, and there are a lot of slag in the rainy season. Coupled with the large amount of water, sundries such as cloth strips and soft plastic products in the water are washed over the grid strips and enter the subsequent structures, which has a great impact on pumps, especially submersible pumps.
(2) There is no fine grid in our factory, and the amount of scum formed by floating objects in the first sedimentation tank is very large, so the labor of operators to remove these scum is very large. In addition, the long-term skimming operation makes a large amount of sewage return to the grid well, which must be lifted twice, increasing the energy consumption of the sewage pump.
(3) Only one grille is a design defect, and the grille fails, so the water supply must be stopped. Therefore, the grid is required to have reliable mud discharge performance. The original grille decontamination machine in this factory is a high chain grille decontamination machine. Because of the material problem of the tooth stripping arm, it is easy to deform, which affects the precision of tooth stripping into the groove and the slag stripping effect is poor, which affects the production.
(4) The factory once installed a fine grid with a grid spacing of 6mm at the outlet of the grit chamber. However, due to the limitation of the site, it is impossible to install the accident crossing device, and the water often runs, which affects the production and is forced to dismantle it. Therefore, it is impossible to add a fine mesh.
In order to solve the above problems, the original high-grate cleaner was updated, and the rotary grate cleaner with the model XGS 1702-4800 and the grid spacing of 10mm produced by Qingyuan Environmental Protection Machinery Factory was installed, which greatly increased the amount of grid slag removal, created good conditions for the operation of submersible pumps, ensured the production requirements and solved the grid of the primary sedimentation tank. Moreover, the electrical control system of the machine is good, which can be cleaned automatically and continuously, at regular intervals and manually, and the operation mode can be changed in different seasons to save energy.
Through practical operation, it is found that the new grille cleaner also has some defects: (1) The rack chain of this machine is made of nylon, which is easy to age and break due to outdoor environment, great temperature changes in winter and summer, sunlight and other reasons. It's very troublesome to replace. The author thinks that the reliability of the equipment is very important, because it runs in an outdoor environment and has no spare grille. Therefore, it is more reliable to use stainless steel as the material of toothpick. (2) Due to the long continuous operation time, the machine is used to salvage the grid slag, which has a great change in weight and the stress of the tooth chain. The stop pads on both sides that play a fixing role are easy to fall off, but the parts are non-standard products and spare parts are difficult. (3) Due to limited space and financial problems, there is no supporting equipment for automatic conveying and pressing of slag, and the labor intensity of workers is high, so the slag cannot fall to the ground. The above defects need to be solved during the transformation of the old factory.
2.2 Problems and solutions of dehydrators There are two dehydrators in our factory, the model is DY2000 belt filter press, and the equipment is the first generation model of the Municipal Environmental Protection Machinery Factory. There are many problems in operation: (1) the filter belt washing device can not meet the actual requirements, and the filter belt washing effect is poor. Cleaning the filter belt is the most critical process of the belt filter press. If the effect is not good, the water-carrying capacity of the filter belt will not be restored, and the dehydration process will not be continued. (2) The design of flocculation reactor needs to be improved. The inlet of the mixed liquid of sludge and medicine is above the reactor, and the reaction is fierce because of the stepped falling and mixing. However, the conditioning reaction between flocculant PAM and sludge is rapid, fragile and irreversible, and the reaction floc is easy to break, and the floc size is not enough in the gravity dewatering section, so it is easy to escape. So the molecular weight of flocculant is too high, and PAM with high molecular weight is more expensive. On the other hand, due to material loss, the output of mud cake is low. (3) Due to the technical problem of mesh weaving at that time, the filter belt interface of the machine was a metal spiral pin ring interface, which caused serious wear of the mud scraper and unclean peeling of mud cakes during operation, which increased the cleaning difficulty of the filter belt and made the service life short. (4) The vacuum drum designed by the original machine is small in aperture, slow in shearing, dewatering and water filtration, poor in effect, easy to leak materials, and the filtrate in the drum is not completely removed, which makes the vacuum drum ineffective and affects the output of mud cakes.
In order to solve practical problems in operation, attention should be paid to overcoming the defects of old equipment when selecting new equipment. The updated dehydrator is DYQ2000 dehydrator, which is characterized by: (1) In the aspect of cleaning the filter belt, the nozzle in the cleaning water tank is a new product, and the naturally formed pressure is greater than that of the old nozzle, which is convenient to disassemble. 1 pipeline booster pump, ISG50-200A, was added when the equipment was installed. The flow rate was 1 1.7m3/h, the lift was 0.45mpa, the flushing water volume was increased from 6m3/h to 9m3/h, and the flushing pressure was increased from 0.4Mpa to 0.7mpa. The flushing effect was good. (2) The number of hollow rollers in the press section was changed from/kloc-0 to 2, and the diameter of the first roller was increased from the original Ф 40 cm to Ф 80 cm, so that the preloading process was easy to realize, so that a large amount of surface free water in sludge flocs quickly squeezed into the filter belt, which reduced the water content of sludge in the press section, reduced the leakage in the extrusion process and significantly improved the output of mud cakes. (3) The structure of flocculation reactor is more reasonable. The mixed liquid of mud and medicine enters from the bottom of the reactor, and a flocculation stirring device is installed in the reactor. The generated floc overflows from the upper opening of the reactor and enters the gravity dewatering section. The strength of the whole reaction process is reduced, and the floc is not easy to break. The actual operation shows that floc formation is good, and the requirement for molecular weight of flocculant PAM is slightly lower than that of the old dehydrator. (4) The filter belt of this machine is seamless and has long service life.
After a period of use, the machine basically overcomes the shortcomings of the old dehydrator, but there are still some problems: (1) The design diameter of the mud inlet pipe is small and it is easy to block. (2) The pipes of dissolution tank and medicine storage tank of auxiliary equipment are easy to be blocked, and the amount of dosing pump is small. The above problems should be improved step by step with the manufacturers.
2.3 Energy-saving measures for equipment
After the plant 1992 was put into use, there were problems of aging equipment and high energy consumption in actual operation. In the operation management of 14, the factory always regards energy saving and consumption reduction as an important topic in management and equipment transformation, and the energy saving transformation of sewage pump and aeration system is the focus of the work.
2.3. 1 sewage pump problems, solutions and effects The sewage pump in our factory was originally designed as four 250WDL vertical pumps, each with a power of 70kw and a water inflow of 1290m3/h (measured). The existing problems are as follows: (1) The water pump manufacturer has stopped production and cannot spare parts. (2) The pump packing is easy to wear, with serious water leakage, sewage splashing, poor hygiene of spare parts in the pump room, high labor intensity, frequent replacement and large maintenance. (3) High energy consumption and low efficiency.
In order to solve the above problems, in 1999, the 4 # sewage pump was replaced by the 44kw submersible pump of the flying pump CP3300LT620, and the measured water inflow was 1330m3/h, which can meet the actual requirements and has good operation effect. The measured energy-saving situation of water pumps, the average results are as follows: Feili pump consumes 760 kwh /d every day, while the old pump consumes 1400 kwh /d, which can save 640 kWh/d. According to the current electricity bill of 0.53 yuan /kwh, a pump can save 339.2 yuan a day and124,300 yuan a year. At present, the renovation of 1 # sewage pump and two reflux pumps has been completed, and the operation effect is very good.
2.3.2 Energy-saving problems of aeration system and the effect of measures. The original design of aeration tank in this factory used perforated pipe aeration device. Due to long service time, serious corrosion, serious blockage and low aeration efficiency. The energy consumption of aeration tank accounts for a large proportion of the energy consumption of the whole sewage plant, which is the focus of energy saving and consumption reduction. In June 2002, the factory transformed the perforated pipes in the west and west corridors of two groups of aeration tanks into silicone rubber tubular aeration pipes, and conducted comparative tests from June 2002 to 2002 10. Under the same experimental conditions, the same blower and the same intake pipe are used, but the aerator is different and the perforated pipe is in the east.
At the same time, the factory measured the actual effect of the blower, and the results showed that the blower used now produced the same air volume and the power consumption was higher than that of similar blowers in the environmental protection equipment market. In the recent transformation of the old factory, the factory will choose low-energy frequency modulation magnetic suspension centrifugal fan to achieve energy-saving effect.
2.4 Foam problem A lot of foam often appears in the aeration tank of this factory in winter, especially when it is cloudy and depressed in winter. Foam floats on the pool surface, overflows the aisle, sometimes it is blown by the wind, flying everywhere, affecting hygiene, sometimes it is even impossible to take samples for testing, and in serious cases it carries activated sludge particles, which affects normal operation.
* * After a special study on the bubble problem, five reasons for the bubble problem were found out, and targeted measures were taken to control the bubble problem in winter. (1) temperature. Due to the low temperature, the bubbles generated in the aeration tank are not easy to rupture and accumulate. At this time, the process should be adjusted to appropriately reduce dissolved oxygen and destroy the foam accumulation conditions. (2) When the content of surfactant in the influent water is high, a large amount of foam is easily generated when it is blown off by air blast. Coupled with temperature conditions, foam accumulation is easy to occur. Therefore, the source of pollution should be identified and measures should be taken to make the inlet water contain no foaming substances and the foam disappear naturally. (3) Because the aerators used in the east and west aeration tanks of this factory are different, they belong to medium bubble type and micro bubble type, and the dissolved oxygen in the west is higher than that in the east for a long time. Due to the small bubbles produced by micropore aeration, it is not easy to break and accumulate, and the foam on the west side of aeration tank in this factory is more serious. The factory took measures to completely dredge the perforated pipe in the east, improved the gas supply efficiency of the perforated pipe, made the dissolved oxygen in the east aeration tank and the west aeration tank approach, and then controlled the foam through appropriate adjustment. (4) In the recent transformation of the old factory, the aerator of the east aeration tank will be transformed, so that both the east and west aeration tanks adopt tubular aerators, which is convenient for the adjustment of dissolved oxygen and improves the oxygen utilization rate. (5) When the MLSS of aeration tank is too low, it is easy to produce foam. Therefore, strictly controlling MLSS above 1.5g/l in winter has obvious effect on controlling foam accumulation.
3. Conclusion
The above is the author's brief analysis of several problems and solutions encountered in the operation and management of this factory, which is a little experience of technical transformation. I hope you can correct me. Due to the serious aging of most structures and equipment, the factory has entered the transformation period. In the future, we will continue to explore the energy-saving potential in technical transformation and operation management on the premise of energy saving, resolutely implement the economic operation indicators approved by Tangshan Drainage Company, and gradually solve the problems and design defects in actual operation through technical transformation, so that the old factory will glow with new vitality.